A microvalve is a valve whose fluid control barrier is less than a millimeter thick, preferably less than 0.5 millimeters thick, and most preferably approximately 0.05 millimeters thick. Thermopneumatic working fluids are used to control microvalves. Thermopneumatically controlled microvalves have been used to control the flow of water and non-corrosive gases over wide ranges of pressure and mass flow conditions.
Attempts to expand the utilization of microvalves have identified problems with existing microvalve designs. For example, existing microvalves cannot be used to control temperature-sensitive fluids, such as refrigerants. This incompatibility stems from a number of factors. For example, existing microvalves are relatively high power devices. In this context, relatively high power devices are devices that operate at 5 Watts or more. High power devices of this type dissipate relatively large amounts of heat, which is transferred to the fluid being controlled. It is important to significantly reduce this problematic heat transfer between a high power microvalve and the temperature sensitive fluid that it controls. It would be highly desirable to develop a low power microvalve, for example, a microvalve that requires less than 2.5 Watts for activation, preferably less than 1 Watt, and most preferably less than 0.5 Watt. In addition to a low-power attribute, the microvalve should preferably withstand a pressure drop and temperature range necessary for new microvalve applications, such as, for the control of refrigerant liquids.